Set-Partitioned QAM Fast-OFDM with Real-Valued Orthogonal Circulant Matrix Transform Pre-Coding

We propose SP-QAM based Fast-OFDM with a novel real-valued OCT pre-coding scheme for IM/DD systems. For 19.76-Gbit/s 20-km transmission, the proposed scheme achieves 3.5-dB sensitivity improvement and higher filtering tolerance over conventional PAM Fast-OFDM.